RandomGraph.java

package emp_proj;

//Zane,Yogi,Nick,Jodie
//TCSS 543
//Nov. 21, 08

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.util.*;

public class RandomGraph {
	
	private static final String NL = "\n";
	
	/**
	 * Entrance point for the program.
	 * java RandomGraph v, e, m, f
	 * @param v - the number of vertices
	 * @param e - the number of edges leaving each node
	 * @param min - the lower bound on the edge capacities
	 * @param max - the upper bound on the edge capacities
	 * @param f - path and file name for saving the graph
	 */
	public static void main(String[] args){
		if(args.length != 5){
			System.out.println("\nInvalid parameters!");
			System.out.println("Usage:");
			System.out.println("java RandomGraph v, e, min, max, f");
			System.out.println("v - the number of vertices in the graph");
			System.out.println("e - the number of edges leaving each node");
			System.out.println("min - the lower bound on edge capacities");
			System.out.println("max - the upper bound on edge capacities");
			System.out.println("f - path and file name for saving this graph");
			System.out.println("Example: java RandomGraph 999 50 75 101 graph1.txt");
		}else if(Integer.parseInt(args[0])> Integer.parseInt(args[1])){
			if(Integer.parseInt(args[3]) >= Integer.parseInt(args[2])){
				toFile(graphBuilder(Integer.parseInt(args[0]),Integer.parseInt(args[1]),Integer.parseInt(args[2]),Integer.parseInt(args[3])),args[4]);
				System.out.println("\nDONE!");
			}else{
				System.out.println("\nFAIL!");
				System.out.println("Max must be greater than or equal to min.");
			}
		}else{
			System.out.println("\nFAIL!");
			System.out.println("The number of vertices must exceed the number of edges leaving each node.");
		}
	}
	
	/**
	 * This method creates a 3 token representation of a graph.
	 * @param v The number of vertices in the graph
	 * @param e The number of edges leaving each vertice
	 * @param min The lowerbound on the capacity value of each edge
	 * @param max The upperbound on the capacity value of each edge
	 * @return A string buffer, each line contains 3 tokens corresponding 
	 *			to a directed edge: the tail, the head, and the capacity.
	 */
	public static StringBuffer graphBuilder(int v, int e, int min, int max){
		int i;
		int j;
		int head;
		int c;
		SortedSet s;
		Random gen = new Random();
		StringBuffer bfr = new StringBuffer();
		
		//Add distinguished node s
		j = 1;
		s = new TreeSet();
		
		while(j <= e){
			head = gen.nextInt(v) + 1;
			if(!s.contains(head)){
				s.add(head);                           // vertex #
				c = min + gen.nextInt(max - min + 1);  // capacity
				bfr.append("s"+" "+"v"+head+" "+c+NL);	
				j++;
			}
		}
		
		//Add distinguished node t
		j = 1;
		s = new TreeSet();
		
		while(j <= e){
			int tail = gen.nextInt(v) + 1;
			if(!s.contains(tail)){
				s.add(tail);							// vertex #
				c = min + gen.nextInt(max - min + 1);
				bfr.append("v"+tail+" "+"t"+" "+c+NL);
				j++;
			}
		}
		
		//Add internal nodes
		for(i = 1; i <= v; i++){
			s = new TreeSet();
			s.add(i);
			j = 1;
			while(j <= e){
				head = gen.nextInt(v) + 1;
				if(!s.contains(head)){
					s.add(head);
					c = min + gen.nextInt(max - min + 1);
					bfr.append("v"+i+" "+"v"+head+" "+c+NL);
					j++;
				}
			}
		}
		return bfr;
	}
	

	/**
	 * This method attempts to save a string at a given location.
	 * @param outString The StringBuffer containing the data being saved
	 * @param filename The complete file path including file name
	 */
	private static void toFile(StringBuffer outString, String filename){
		try{
			BufferedWriter fout = new BufferedWriter(new FileWriter(filename));
			fout.write(outString.toString());
			fout.close();
		}catch(Exception e){
			System.out.println("Error saving file.");
			System.out.println("Please check file paths and restart this program.");
			System.exit(1);
		} 
	}
}